Method of broadcasting data by a multicast source with broadcasting of an identifier of the broadcasting strategy in a multicast signalling channel

ABSTRACT

A method of broadcasting data from a multicast source (S) to a plurality of receivers (CL) in a telecommunications network ( 1 ) in accordance with a broadcasting strategy, including: a step (E 40 ) of receiving parameters (STAT, AG, CS); a step (E 50 ) of adjusting said strategy as a function of said parameters; and in the event of modification of said strategy, a step (E 70 ) of broadcasting in a multicast signaling channel, an identifier of this new broadcasting strategy.

RELATED APPLICATIONS

This is a U.S. National Phase Application under 35 USC §371 ofInternational Application PCT/FR2009/051776, filed on Sep. 22, 2009.

This application claims the priority of French application Ser. No.08/56562 filed on Sep. 30, 2008, the content of which is herebyincorporated by reference.

BACKGROUND OF THE INVENTION

The field of the present invention is that of telecommunicationsnetworks known as “multibroadcast” networks in which a source is able tobroadcast data to a plurality of destinations.

In such networks, routers construct a replication tree between thesource and the destinations with the result that a data packet passesonly once over each link of the network and is replicated by the routersto reach each of the destinations.

This kind of broadcasting technique is known as a “multicast” technique.

Using such a replication tree allows massive broadcasting of informationwith maximum optimization of the network resources.

In contrast, multicast broadcast networks are known to be inherentlyunreliable because the data is transported under the UDP protocol, i.e.in non-connected mode.

The document “P2P Multicast Library” available athttp://pml.sourceforge.net/Technology/ proposes a method of making amulticast network reliable in which destinations of a broadcast streamare able to recover fragments of the stream that they have not receivedfrom peers of a peer-to-peer network.

In that method, a source of the peer-to-peer network sends the variousdestinations a message including the characteristics of a strategy forbroadcasting of the data by that source.

That method has a major drawback in that it is necessary, as is usual inpeer-to-peer networks, for the source to know the destinations to whichit must send these strategy characteristics.

Furthermore, a method of that kind requires that the sending of thestrategy characteristics be secure, for example through the use of anerror correction code mechanism or a specific protocol by means of whichthe destinations may request resending of the strategy characteristics,either of which solutions is liable to cause great congestion in thenetwork if the number of destinations or the frequency of changes ofstrategy by the source increases.

SUMMARY OF THE INVENTION

One aspect of the invention is directed to a method of broadcasting datafrom a multicast source to a plurality of receivers in atelecommunications network in accordance with a broadcasting strategy.

This method includes:

-   -   a step of receiving parameters;    -   a step of adjusting the broadcasting strategy as a function of        said parameters; and    -   in the event of modification of said strategy, a step of        broadcasting in a multicast signaling channel an identifier of a        new broadcasting strategy.

Another aspect of the invention is directed to a source of databroadcast to a plurality of receivers in a telecommunications networkaccording to a broadcasting strategy, this source including:

-   -   means for receiving parameters;    -   means for adjusting the broadcasting strategy as a function of        said parameters; and    -   means for broadcasting in a multicast signaling channel an        identifier of a new broadcasting strategy.

Generally speaking, the invention provides for adjusting the strategyfor broadcasting of data by the sources as a function of parameters fedback to the sources.

In the present document, the strategy for broadcasting of data by asource is defined by the number of streams used by that source and thecharacteristics of each of those streams.

According to an embodiment of the invention, after each strategymodification, the source broadcasts an identifier of the new strategy ona multicast signaling channel in order to inform the receivers of it.

By means of this feature, it is not necessary for the source to know thedestination of the change of strategy information.

Moreover, sending a strategy identifier rather than the characteristicsof the strategy itself has the advantage of avoiding the provision of aspecific security mechanism making the destinations responsible forrecovering the strategy themselves in unicast messages that areinherently secure.

According to an embodiment of the invention, the parameters fed back tothe sources may be of different kinds.

For example, it may be a question of statistics on the reception offragments of the data by one or more receivers, which statistics mayrelate to the number of fragments received or to the number of fragmentsnot received.

It may also be a question of the bit rates at which one or morereceivers expect to receive.

It may further be a question of an aggregate data item (for example anaverage) comprising bit rates at which a plurality of receivers expectto receive.

In the above three situations, the source itself defines its newstrategy on the basis of the received parameters and implements it afterbroadcasting an identifier of the new strategy in the multicastsignaling channel.

According to an embodiment of the invention, the parameters fed back tothe source may also be characteristics of the new strategy. In thissituation, the source does not define the new strategy itself, butapplies that which is imposed on it.

Another aspect of the invention is directed to a method of supervisingthe broadcasting of data sent by a multicast source to a plurality ofreceivers in a telecommunications network in accordance with abroadcasting strategy.

This method includes:

-   -   a step of sending at least one of said receivers information        relating to the source, said information including an        identification of a multicast signaling channel associated with        the source intended to broadcast an identifier of said strategy;    -   a step of obtaining from at least one of the receivers        statistics on reception by said receiver of fragments of the        data broadcast by the source according to said strategy;    -   a step of obtaining parameters from said statistics, the        parameters including:        -   an aggregate data item including receiving bit rates            expected by a plurality of the receivers; or        -   characteristics of a new strategy for broadcasting said            data; and    -   a step of sending the parameters to the source.

Another aspect of the invention is directed to a supervisor of thebroadcasting of data sent by a multicast source to a plurality ofreceivers in a telecommunications network in accordance with abroadcasting strategy, the supervisor including:

-   -   means for sending at least one of said receivers information        relating to the source, said information including an        identification of a multicast signaling channel associated with        the source intended to broadcast an identifier of said strategy;    -   means for obtaining from at least one of said receivers        statistics on reception by said receiver of fragments of the        data broadcast by the source in accordance with said strategy;    -   means for obtaining parameters from said statistics, said        parameters including at least:        -   an aggregate data item (AG) including receiving bit rates            (EXP_DB) expected by a plurality of said receivers; or        -   characteristics (CS) of a new strategy for broadcasting said            data; and    -   means for sending the parameters to the source.

According to an embodiment of the invention, a supervisor is introducedthat is responsible for collecting from a plurality of receiversstatistics on the reception of fragments of data and for defining, onthe basis of those statistics, the parameters to be fed back to asource.

Those parameters include an aggregate data item representing bit ratesat which a plurality of receivers expect to receive, the source beingresponsible for defining its broadcasting strategy on the basis of thisaggregate data item or characteristics of the new strategy defined bythe supervisor and imposed on the source.

In one particular implementation of the invention, the supervisionmethod includes:

-   -   a step of obtaining the maximum number of streams broadcast        simultaneously in the network; and    -   a step of sending that number to the source.

This feature advantageously limits the number of multicast streamsbroadcast simultaneously in the network.

On reception of such information, a broadcast source is able to modifyits strategy to limit the number of streams that it sends so as toguarantee that the total number of multicast streams broadcast in thenetwork does not exceed this maximum number.

In one particular implementation of the invention, the supervisionmethod includes:

-   -   a step of sending a request to a router of the network for it to        monitor the subscription of the receivers connected to that        router to the multicast streams broadcast in the network.

Another aspect of the invention is directed to a method of receiving atleast one data stream broadcast by at least one multicast source in atelecommunications network in accordance with a broadcasting strategy,the method including:

-   -   a step of detecting in a multicast signaling channel broadcast        by a source of the data an identifier of a new broadcasting        strategy used by the source; and    -   a step of using a new strategy for receiving said data.

Another aspect of the invention is directed to a receiver of at leastone data stream broadcast by at least one multicast source in atelecommunications network in accordance with a broadcasting strategy,this receiver including:

-   -   means for detecting in a multicast signaling channel broadcast        by a source of said data an identifier of a new broadcasting        strategy used by the source; and    -   means for implementing a new strategy for receiving the data.

In one particular implementation, this method includes a step of sendingstatistics on the reception of stream fragments to a broadcastsupervisor of the invention.

In one particular embodiment of the invention, the receiver also sendsthe above-mentioned entity an ideal receiving bit rate required by thereceiver.

In one particular embodiment of the invention, the receiver obtains atleast one data fragment from a peer of a peer-to-peer network.

In one particular embodiment of the invention, to define the newstrategy for receiving said data:

-   -   the receiver evaluates at least one rate of loss of said data on        said at least one stream; and    -   the receiver unsubscribes from at least one of said streams if        said loss rate exceeds a predetermined threshold.

The particular features and advantages of the data source, thesupervisor, and the receiver of the invention are similar to those ofthe data broadcasting method, the supervision method, and the receivingmethod referred to above.

In one particular implementation, the various steps of the broadcasting,supervision, and receiving methods are determined by instructions ofcomputer programs.

Other aspects of the invention include:

-   -   a computer program on an information medium, this program being        adapted to be used in a multicast source or more generally in a        computer, this program including instructions for executing the        steps of a broadcasting method as described above;    -   a computer program on an information medium, this program being        adapted to be used in a multicast supervisor or more generally        in a computer, this program including instructions for executing        the steps of a supervision method as described above; and    -   a computer program on an information medium, this program being        adapted to be used in a receiver or more generally in a        computer, this program including instructions for executing the        steps of a receiving method as described above.

These programs may use any programming language and take the form ofsource code, object code or a code intermediate between source code andobject code, such as a partially-compiled form, or any other desirableform.

Another aspect of the invention is directed to a storage medium readableby a computer and including instructions of a computer program forexecuting the steps of the broadcasting method referred to above.

Another aspect of the invention is directed to a storage medium readableby a computer and including instructions of a computer program forexecuting the steps of the supervision method referred to above.

Another aspect of the invention is directed to a storage medium readableby a computer and including instructions of a computer program forexecuting the steps of the receiving method referred to above.

Each of the above information media may be any entity or device capableof storing the program. For example, the medium may include storagemeans, such as a read-only memory (ROM), for example a compact disk (CD)ROM or a micro-electronic circuit ROM, or magnetic storage means, forexample a floppy disk or a hard disk.

Moreover, each of these information media may be a transmissible mediumsuch as an electrical or optical signal, which may be routed via anelectrical or optical cable, by radio or by other means. The program ofthe invention may in particular be downloaded over an Internet-typenetwork.

Alternatively, each of these information media may be an integratedcircuit in which the program is incorporated, the circuit being adaptedto execute the method in question or to be used in its execution.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the present invention emerge from thedescription given below with reference to the appended drawings, whichshow one non-limiting embodiment of the invention. In the figures:

FIG. 1 represents a supervisor and a plurality of sources and receivers;

FIG. 2 represents the hardware architecture of a source;

FIG. 3 represents the hardware architecture of a receiver;

FIG. 4 represents the hardware architecture of a supervisor; and

FIG. 5 represents the principal steps of the broadcasting, supervision,and receiving methods.

DETAILED DESCRIPTION OF ONE EMBODIMENT

FIG. 1 illustrates use of the invention to multibroadcast a data content(CONT) from multicast sources S to customer receivers CL in atelecommunications network 1.

The content CONT is generally stored in a file. If a multicast source Sor a customer receiver CL has a limit on the size of files that it canmanipulate, this file may be divided into a plurality of blocks in orderto be able to broadcast it. Otherwise, the content CONT consists of onlyone block.

In the embodiment described here, a customer receiver CL is required tobe able to verify the integrity of received data and each block isdivided into one or more fragments, the size of a fragment being definedas a function of the mechanism used to verify its integrity.

At the most atomic level, each fragment is divided into segments. Asegment may be encapsulated in a UDP packet to be broadcast in thenetwork 1 by a multicast source S.

According to the invention, broadcasting a data content CONT may involveone or more multicast sources S, each source using one or more multicaststreams.

The number of streams used by a multicast source S and thecharacteristics of each of those streams define the multibroadcastingstrategy of the source S. Each strategy has a sequence number SEQ thatuniquely identifies it.

In this example, a multicast supervisor SUP_MC informs the customerreceivers CL of the multicast sources S and the streams broadcast bythose sources. To this end, in the embodiment described here, themulticast supervisor SUP_MC includes a list LS of the multicast sourcesS and the streams FL broadcast by those sources.

In the embodiment described here, a multicast source S has the hardwarearchitecture of a conventional computer, as represented in FIG. 2.

This kind of multicast source S includes a processor 11, a random-accessmemory (RAM) 12, and a read-only memory (ROM) 13. This read-only memory13 constitutes a storage medium of the invention, readable by themulticast source S, in which is stored a computer program of theinvention, that program including instructions for executing the stepsof a broadcasting method of the invention, the principal steps E10 toE70 of that method being represented in FIG. 5.

The multicast source S includes means for registering with the multicastserver SUP_MC.

According to the invention, the multicast source S may vary itsbroadcasting strategy while broadcasting a data content D.

In the embodiment described here, the multicast source S includes arewritable non-volatile flash memory 15 in which it stores the elementsELT defining its current multibroadcasting strategy.

The multicast source S also includes means 14 for communicating via thenetwork 1, enabling it in particular to receive data sent by themulticast supervisor SUP_MC and to broadcast over the network:

-   -   a heartbeat signaling stream multicast by the source S and to        which the customer receivers CL may subscribe; and    -   at least one content stream that carries elements enabling the        customer receivers CL to determine the position of the data        received in the data content CONT (fragment number, segment        number within the fragment).

According to the invention, when a multicast source S changes strategy,it modifies the sequence number SEQ sent in the heartbeat multicastsignaling channel to advise the customer receivers CL of the change.

According to the invention, a multicast source S informs the multicastsupervisor SUP_MC of any change of strategy by sending it the updatedelements ELT, these including the adjusted characteristics INF_FL ofeach of the streams sent by that source S and the characteristics CHB ofits heartbeat signaling stream.

In the embodiment described here, the customer receivers CL also havethe hardware architecture of a conventional computer, as represented inFIG. 3.

This kind of customer receiver CL includes a processor 21, arandom-access memory (RAM) 22, and a read-only memory (ROM) 23. Thisread-only memory 23 constitutes a storage medium of the invention,readable by the customer receiver CL, on which is stored a computerprogram of the invention including instructions for executing the stepsof a receiving method of the invention, the principal steps G10 to G80of that method being represented in FIG. 5.

The customer receiver CL also includes means 24 for sending data to themulticast supervisor SUP_MC or for consulting it obtain a list of themulticast sources S and the characteristics ELT of the streams FLbroadcast by those sources. In the embodiment described here, thecommunications means 24 use the HTTP protocol and the requests to themulticast supervisor SUP_MC are HTTP GET messages.

The customer receiver CL includes means 25 for implementing the IGMPmulticast access protocol, these means enabling this customer tosubscribe to the traffic sent by a multicast source S so as to receivethe heartbeat signaling multicast stream and the content stream orstreams broadcast by that source S. These means are known to the personskilled in the art and are not described in detail here.

According to the invention, the customer receiver CL is able to detect achange of sequence number SEQ in the heartbeat multicast signalingstream and to interpret such a change as representing a change ofbroadcasting strategy by the multicast source S sending that stream.Following such detection, the customer receiver CL of the invention isable to consult the multicast supervisor MC to obtain the elements ELTof the new strategy.

In the embodiment described here at least some customer receivers CL arepeers of a peer-to-peer network 2.

These receivers CL use communications means 26 to communicate with eachother over the peer-to-peer network to exchange fragments of the contentCONT that they have received either directly from other peers (inunicast mode) or as multibroadcast by one or more multicast sources S.They are also able to verify the integrity of these fragments.

To this end they may for example use a reliability enhancement method asdescribed in the document WO 2007/085763.

In the embodiment described here, the peer-to-peer network 2 is a filedistribution network of the file swarming type using the BitTorrentprotocol or a similar protocol and in which each customer receiver CLthat is a peer of this network can send the other peers file fragmentseven before receiving the file completely.

In this embodiment, the system of the invention includes a unicastsupervisor SUP_CC with which a customer receiver CL may register toobtain a list of other peers of the peer-to-peer network 2 with which itmay communicate to exchange file fragments corresponding to a givencontent.

The customer receivers CL of the invention include means for regularlysending the multicast supervisor SUP_MC statistics STAT on the receptionof the content and possibly an ideal receiving bit rate EXP_DB. In theembodiment described here, these statistics STAT include a list offragments received by this customer receiver CL and a list of fragmentsnot received by this customer receiver CL.

These statistics STAT relate at least to the fragments broadcast by themulticast sources S. If a customer receiver CL is also a peer of thepeer-to-peer network 2, these statistics STAT also relate to thefragments received in unicast mode from other peers.

According to the invention, the customer receiver CL includes means 21,22, 23 for defining and modifying its receiving strategy. These meansare further described below with reference to the step G80 of thereceiving method used by this receiver.

In the embodiment described here, the multicast supervisor SUP_MC alsohas the hardware architecture of a conventional computer, as representedin FIG. 4.

It includes a processor 31, a random-access memory (RAM) 32, and aread-only memory (ROM) 33. This read-only memory 33 constitutes astorage medium of the invention, readable by the multicast supervisorSUP_MC, on which is stored a computer program of the invention includinginstructions for executing the steps of a supervision method of theinvention, the principal steps F10 to F80 of that method beingrepresented in FIG. 5.

The multicast supervisor SUP_MC includes means for registering amulticast source having one or more streams to transmit. To this end, inthe embodiment described here, it manages a database BD_REG thatincludes for each registered multicast source S the parameters of theheartbeat signaling streams and the characteristics of the data streamssent by that source.

In one particular embodiment of the invention, the elements ELT sent bya multicast source S to the multicast supervisor SUP_MC for registrationpurposes are:

-   -   the sequence number SEQ of the sending strategy;    -   information CHB on the heartbeat channel of the source S, for        example the heartbeat multicast IP address, the destination UDP        port, and the period; and    -   for each stream sent by the source S, information INF_FL on that        stream including for example the multicast destination IP        address of that stream, the destination UDP port, the bit rate,        the fragment numbers at the start and at the end of the        sequence, and a time reference enabling a customer receiver CL        to calculate approximately when an item of data will be sent.

In the embodiment described here, the multicast supervisor SUP_MC storesthese new elements ELT in the database BD_REG.

In the embodiment described here, the multicast supervisor SUP_MCincludes means 24 for communicating over the network 1, enabling it inparticular to communicate with a multicast source S using the TCPprotocol.

In the embodiment described here, the multicast supervisor SUP_MC usesthese means 24 to set up a communications channel C1 with each multicastsource S registered with it.

According to the invention, the multicast supervisor SUP_MC includesmeans for receiving from at least one customer receiver CL statisticsSTAT on the fragments received or not received by that customerreceiver, possibly the ideal multicast receiving bit rate EXP_DB forthat customer receiver CL, and information INF_S on the multicastsources S from which this customer receiver CL receives the heartbeatsignaling streams.

In the embodiment described here, the multicast supervisor SUP_MC storesthis information in a database BD_STAT.

In the embodiment described here, the communications means 34 of thesupervisor SUP_MC enable it to monitor the routers R of the network 1 tolimit the maximum number NB_FL of multicast streams broadcastsimultaneously in the network 1.

According to the invention, the multicast supervisor SUP_MC includesmeans 31, 32, 33 for aggregating in an aggregate data item AG the idealbit rate EXP_DB, possibly the statistics STAT, and the information INF_Son the multicast sources.

In the embodiment described here, the aggregate data item AG created bythe multicast supervisor SUP_MC for a multicast source S and aparticular content includes:

-   -   the number NR of customer receivers CL receiving that content;    -   the number NHB of customer receivers CL receiving the heartbeat        stream from that source;    -   reception statistics FGST including for example, for each        fragment FG, the number of customer receivers CL that have        received that fragment and the heartbeat from the source;    -   one or more ideal bit rates EXP_DB expected by the customer        receivers CL;    -   the maximum bit rate MAX_DB of the streams advertised by the        customer receivers CL; and possibly    -   the number NB_FL of streams that the multibroadcasting network        can support.

In the embodiment described here, the aggregate data item AG is storedin the database BD_STAT.

According to the invention, the multicast supervisor SUP_MC includesmeans for making this aggregate data item AG available to the multicastsource S concerned. In the embodiment described here, the multicastsupervisor SUP_MC sends the aggregate data item AG to a multicast sourceS in the communications channel C1 set up between the multicastsupervisor SUP_MC and the source S by its communications means 34.

In another embodiment, the multicast supervisor SUP_MC sends a multicastsource S the characteristics CS of the strategy that it is to deploy.

According to the invention, a multicast source S includes means foradjusting its sending strategy as a function of aggregate data items AGreceived from the multicast supervisor SUP_MC and possibly strategycharacteristics CS indicated thereby.

FIG. 5 represents diagrammatically a data multibroadcasting sessionusing the invention.

During a step E10, a multicast source S registers with the multicastsupervisor SUP_MC, sending it the elements ELT including the parametersCHB of the heartbeat flux and the characteristics SEQ, INF_FL of eachstream that it sends. This information is stored by the multicastsupervisor SUP_MC in the database BD_REG during a step F10.

The multicast supervisor SUP_MC and the multicast source S then set up acommunications channel C1 on which they are able to communicate usingthe TCP protocol, respectively during a step F20 and a step E20. In theembodiment described here, this channel C1 is set up at the initiativeof the supervisor SUP_MC.

It is assumed that at least one customer receiver CL consults themulticast supervisor SUP_MC during a step G10 to obtain the list of themulticast sources S broadcasting a content CONT of interest to it. Inthe embodiment described here, this consultation is effected by means ofthe HTTP message GET. The customer receiver preferably indicates in thisrequest the maximum receiving bit rate accepted by this customer.

On reception of such a request, the multicast supervisor SUP_MCcommunicates to the customer receiver CL during a step F30 the multicastsources S broadcasting with a bit rate acceptable to the customerreceiver CL and, for each of those sources, the information CHB on theheartbeat signaling channel of the source and the information INF_FL oneach stream broadcast by that source.

It is assumed that the multicast source S begins to broadcast during astep E30:

-   -   its heartbeat stream; and    -   one or more content streams, in accordance with its strategy as        defined by the elements ELT that it communicated to the        multicast supervisor SUP_MC in the step E10 at registration        time.

To receive data broadcast by a multicast source S, a customer receiverCL subscribes during a step G20 to the heartbeat signaling channel andto one or more streams broadcast by that source S, the multicastsupervisor SUP_MC having communicated the information on these variousstreams to it during the step F30.

It is assumed in this example that a customer receiver CL is a peer ofthe peer-to-peer network 2 and is also seeking to be able to exchangefragments of the content CONT with other peers of this network.

To this end, the peer registers with the unicast supervisor SUP_UCduring a step G30 and obtains from that server a list of peers of thepeer-to-peer network 2 seeking to exchange fragments of this content.

In the embodiment described here, during a step F40 the supervisorSUP_MC sends a request RQ to a router R of the network for that routerto monitor the subscription of the receivers that are connected to it tothe multicast streams broadcast in the network. To be more precise, thissubscription monitoring consists in verifying that a receiver does notaccess streams other than those to which it subscribed during the stepG20.

Then, during a step F45, supervisor SUP_MC obtains the maximum numberNB_FL of streams that can be broadcast simultaneously in the network.

According to the invention, a customer receiver CL regularly sends themulticast supervisor SUP_MC during a step G40 the statistics STAT on thefragments received or not received by that customer receiver CL, theideal multicast receiving bit rate EXP_DB for that customer receiver CL,and information INF_S on the multicast sources S from which thiscustomer receiver CL receives the heartbeat streams. The multicastsupervisor SUP_MC receives and stores these statistics in the databaseBD_STAT during a step F50.

During a step F60, the multicast supervisor SUP_MC aggregates in anaggregate data item AG the statistics STAT, the ideal bit rate EXP_DBexpected by each receiver, the maximum number of streams NB_FL that thenetwork 1 is able to support, and the information on the multicastsources. The multicast supervisor SUP_MC stores this aggregate data itemAG in the database BD_STAT during this same step F60.

Then, during a step F70, the multicast supervisor SUP_MC sends theaggregate data item AG via the channel C1 set up with the source Sconcerned to that source so that the latter source is able to adjust itsstrategy. Alternatively, it imposes a strategy on it by communicating toit the characteristics CS of the latter strategy. This aggregate dataitem AG or the strategy characteristics CS are received by the sourceduring a step E40.

The multicast source S adjusts its strategy during a step E50 as afunction of the aggregate data item or the characteristics of thestrategy CS defined by the supervisor.

As soon as it modifies its sending strategy, the multicast source Ssends the multicast supervisor SUP_MC during a step E60 the elements ELTof the updated new strategy, including the adjusted characteristicsINF_FL of each of the streams sent by the source S and thecharacteristics CHB of its heartbeat stream.

These updated elements ELT are stored by the multicast supervisor SUP_MCduring a step F80.

Simultaneously, during a step E70, the multicast source S modifies thesequence number SEQ sent in the heartbeat signaling stream that it isbroadcasting to inform the customer receivers CL of its change inbroadcasting strategy.

The customer receiver CL detects the new sequence number during a stepG60 of its receiving method.

It may then decide during a step G80 to modify its receiving strategy bysubscribing to new multicast broadcasting channels (discovered byconsulting the multicast supervisor SUP_MC during a step G70), byunsubscribing from some multicast channels or by looking for somemissing fragments on the peer-to-peer network 2.

To define its receiving strategy, a customer receiver CL preferablydetects the multibroadcast streams that it is able to receive,subscribes to those streams, detects segments received incorrectly inthose streams, waits a particular time in the hope of receiving themissing segments following the change of strategy of one or moremulticast sources, and as a last resort obtains the missing segmentsfrom the peers of the peer-to-peer network 2.

In one particular embodiment of the invention, if a customer receiverdetects a high number of lost packets, it unsubscribes from one or moremulticast streams. This characteristic has the advantage of making itpossible to control congestion in the multicast network 1 by preventinga customer receiver CL subscribing to a number of streams that is toohigh given the capacities of the network 1.

To this end, in one particular embodiment of the invention a customerreceiver CL determines the total segment loss rate and the loss rate perstream.

If the loss rate relates to only one or some streams, it is probablethat the network is a congestion between the multicast source S of thatstream and the customer receiver CL. In this situation the customerreceiver CL could unsubscribe from this stream temporarily, hoping thatthe congestion disappears.

However, if the loss rate is distributed across all the streams, thecustomer receiver CL reduces the number of streams to which itsubscribes and seeks to obtain the missing fragments from the peers ofthe network 2.

As explained above, the invention has the advantage that it makes itpossible to modify the strategies for broadcasting of a content by amulticast source.

In a manner that is not limiting on the invention, the invention may usethe following broadcasting strategies:

-   -   single-stream strategy: in this strategy the source broadcasts        all the content in loop mode in a single stream; and    -   simple phase-shifted multistream strategy: this strategy is        applied if a source has all of the content to be broadcast when        broadcasting starts; the source constructs N streams (N being        the maximum number of streams determined by configuring the        source), each broadcasting the whole of the content with a        time-shift at the ideal bit rate indicated by the multicast        supervisor SUP_MC.

The invention claimed is:
 1. A method of broadcasting data from amulticast source to a plurality of receivers in a telecommunicationsnetwork, wherein said source performs a process comprising: broadcastingdata and an identifier, the data being broadcast in accordance with afirst broadcasting strategy identified by the identifier; receiving,from a supervisor, parameters relating to the broadcasting of data bythe source; adjusting said first broadcasting strategy as a function ofsaid parameters to obtain a new broadcasting strategy; and broadcastingin a multicast signaling channel, an identifier of the new broadcastingstrategy, wherein each of the first strategy and the new strategy takeinto account factors comprising the number of streams used by a sourceand the characteristics of each of those streams.
 2. The broadcastingmethod according to claim 1, wherein said parameters include at leastone of the elements belonging to the group comprising: statistics onreception of fragments of said data by at least one of said receivers; areceiving bit rate expected by at least one of said receivers; a maximumnumber of streams that said network is able to support; an aggregatedata item including receiving bit rates expected by a plurality of saidreceivers; and characteristics of said new broadcasting strategy definedby the supervisor.
 3. A computer program including instructions forexecuting the data broadcasting method according to claim 1 when saidprogram is executed by a computer.
 4. A method of supervising thebroadcasting of data sent by a multicast source to a plurality ofreceivers in a telecommunications network in accordance with abroadcasting strategy, wherein a supervisor performs a processcomprising: sending, to at least one of said receivers, informationrelating to the source, said information including an identification ofa multicast signaling channel associated with the source intended tobroadcast an identifier of said strategy; obtaining, from the receiver,statistics concerning the reception, by said receiver, of fragments ofsaid data broadcast by the source in accordance with said strategy;obtaining, from the obtained statistics, parameters including: anaggregate data item including receiving bit rates expected by aplurality of said receivers; or characteristics of a new strategy,defined by the supervisor, for broadcasting said data; and sending saidparameters to said source, wherein each of the first strategy and thenew strategy take into account factors comprising the number of streamsused by a source and the characteristics of each of those streams. 5.The supervision method according to claim 4, comprising: obtaining themaximum number of streams broadcast simultaneously in said network; andsending that number to said source.
 6. The supervision method accordingto claim 4, comprising: sending a request to a router of said networkfor it to monitor the subscription of the receivers broadcast connectedto that router to the multicast streams broadcast in said network.
 7. Acomputer program including instructions for executing the data receivingmethod according to claim 6 when said program is executed by a computer.8. A computer program including instructions for executing thesupervision method according to claim 4 when said program is executed bya computer.
 9. A method of receiving at least one data stream broadcastby at least one multicast source in a first telecommunications networkin accordance with a broadcasting strategy, wherein at least onereceiver performs a process comprising: receiving, by means of amulticast signaling channel, data and an identifier, the data beingbroadcast by the at least one source in accordance with a firstbroadcasting strategy identified by the identifier; sending, to abroadcast supervisor of said network, statistics concerning thereception, by said receiver, of fragments of said data broadcast by thesource in accordance with said strategy; detecting, in the multicastsignaling channel broadcast by the source of said data, an identifier ofa new broadcasting strategy used by said source; obtaining the newbroadcasting strategy; and using the new strategy for receiving saiddata, wherein each of the first strategy and the new strategy take intoaccount factors comprising the number of streams used by a source andthe characteristics of each of those streams.
 10. The receiving methodaccording to claim 9, comprising obtaining at least one fragment of saiddata from a peer of a peer-to-peer network.
 11. The receiving methodaccording to claim 9, wherein to define the new strategy for receivingsaid data: at least one rate of loss of said data on said at least onestream is evaluated; and at least one of said streams is unsubscribedfrom if said loss rate exceeds a predetermined threshold.
 12. A sourceof data broadcast to a plurality of receivers in a telecommunicationsnetwork, the source comprising: means for broadcasting data and anidentifier, the data being broadcast in accordance with a firstbroadcasting strategy identified by the identifier; means for receiving,from a supervisor, parameters relating to the data broadcasting; meansfor adjusting said first broadcasting strategy as a function of saidparameters to obtain a new broadcasting strategy; and means forbroadcasting, in a multicast signaling channel, an identifier of the newbroadcasting strategy, wherein each of the first strategy and the newstrategy take into account factors comprising the number of streams usedby a source and the characteristics of each of those streams.
 13. Asupervisor of the broadcasting of data sent by a multicast source to aplurality of receivers in a telecommunications network in accordancewith a broadcasting strategy, said supervisor comprising: means forsending, to at least one of said receivers, information relating to thesource, said information including an identification of a multicastsignaling channel associated with the source intended to broadcast anidentifier of said strategy; means for obtaining, from at least one ofsaid receivers, statistics concerning the reception, by said receiver,of fragments of said data broadcast by the source in accordance withsaid strategy; means for obtaining, from the obtained statistics,parameters including: an aggregate data item including receiving bitrates expected by a plurality of said receivers; or characteristics of anew strategy, defined by the supervisor, for broadcasting said data; andmeans for sending said parameters to said source, wherein each of thefirst strategy and the new strategy take into account factors comprisingthe number of streams used by a source and the characteristics of eachof those streams.
 14. A receiver of at least one data stream broadcastby at least one multicast source in a first telecommunications networkin accordance with a broadcasting strategy, said receiver comprising:means for receiving, by means of a multicast signaling channel, data andan identifier, the data being broadcast by the at least one source inaccordance with a first broadcasting strategy identified by theidentifier; means for sending, to a broadcast supervisor of saidnetwork, statistics concerning the reception, by the receiver, offragments of data of said stream; means for detecting, in the multicastsignaling channel broadcast by the source of said data, an identifier ofa new broadcasting strategy used by said source; means for obtaining thenew broadcasting strategy; and means for implementing the new strategyfor receiving said data, wherein each of the first strategy and the newstrategy take into account factors comprising the number of streams usedby a source and the characteristics of each of those streams.
 15. Asource of data broadcast to a plurality of receivers in atelecommunications network, said source comprising: a componentconfigured to broadcast data and an identifier, the data being broadcastin accordance with a first broadcasting strategy identified by theidentifier; a component configured to receive, from a supervisor,parameters relating to the data broadcasting; a component configured toadjust said first broadcasting strategy as a function of said parametersto obtain a new broadcasting strategy; and a component configured tobroadcast, in a multicast signaling channel, an identifier of the newbroadcasting strategy, wherein each of the first strategy and the newstrategy take into account factors comprising the number of streams usedby a source and the characteristics of each of those streams.
 16. Asupervisor of the broadcasting of data sent by a multicast source to aplurality of receivers in a telecommunications network in accordancewith a broadcasting strategy, said supervisor comprising: a componentconfigured to send, to at least one of said receivers, informationrelating to the source, said information including an identification ofa multicast signaling channel associated with the source intended tobroadcast an identifier of said strategy; a component configured toobtaining, from at least one of said receivers, statistics concerningthe reception, by said receiver, of fragments of said data broadcast bythe source in accordance with said strategy; a component configured toobtain, from the obtained statistics, parameters including: an aggregatedata item including receiving bit rates expected by a plurality of saidreceivers; or characteristics of a new strategy, defined by thesupervisor, for broadcasting said data; and a component configured tosend said parameters to said source wherein each of the first strategyand the new strategy take into account factors comprising the number ofstreams used by a source and the characteristics of each of thosestreams.
 17. A receiver of at least one data stream broadcast by atleast one multicast source in a first telecommunications network inaccordance with a broadcasting strategy, said receiver comprising: acomponent configured to receive, by means of a multicast signalingchannel, data and an identifier, the data being broadcast by the atleast one source in accordance with a first broadcasting strategyidentified by the identifier, a component configured to send, to abroadcast supervisor of said network, statistics concerning thereception, by said receiver, of fragments of said data broadcast by thesource in accordance with said strategy; a component configured todetect, in the multicast signaling channel broadcast by a source of saiddata, an identifier of a new broadcasting strategy used by said source;a component configured to obtain the new broadcasting strategy, and acomponent configured to implement the new strategy for receiving saiddata, wherein each of the first strategy and the new strategy take intoaccount factors comprising the number of streams used by a source andthe characteristics of each of those streams.